stepper motor

hi i am totally new to robotics. i am planning to do a project in it although. i am trying to build a robot that will go in a spiral path starting
from centre and after each 3 cm or 1 inch it will drop an object from it i was told to use a stepper motor cos speed of the robot can be controlled nicely with it... i hav already got a stpper motor which can carry around 2 to 3 kg of weight (i forgot its torque). basically i am stuck at the point as to how to make a stepper motor driver and what all are the basic requirements for the stepper motor to work? please reply asap as i am in urgent need of it.... if u have any links or any pdf's or images that can help me understand this concept please forward it to me at snipped-for-privacy@gmail.com
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On Sat, 12 Mar 2011 23:52:01 -0800 (PST), Roshan Nagekar

Projects like this always work out *so* well. Read and understand the material at <http://www.cs.uiowa.edu/~jones/step/> first.
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Rich Webb Norfolk, VA

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hey Rich thanks for the reply can u share any such link which could explain this stuff to me in a layman's language?
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On Sun, 13 Mar 2011 06:03:54 -0700 (PDT), Roshan Nagekar

That site pretty much is, at least if you're considering designing your own controller. An alternative would be something like <http://www.robotshop.com/cytron-3-40v-2a-unipolar-bipolar-stepper-motor-controller.html
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Rich Webb Norfolk, VA

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Roshan, that link is about as close to "layman's language" as you can get and still explain how stepper motors work and how to use them. If it's over your head, then you probably don't have the background you need to design and build your own robot from scratch. You might try to get one of the simple programmable robot kits like the Lego Mindstorms or VEX and built your robot from that instead. You don't need any real background in electrical engineering to work with kits like those.
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Firstly, you need two motors on a robot platform put side by side or a car arrangement with one driving motor plus a steering linkage turned by motor. Anyway, you need two motors.
Stepper motors are recommended only if your load stays contant (one constant weight) and you are not going to support external disturbances (hitting a wall or moving on uneven terrain) If you are not a good electronic hobbyist, I suggest you buy the stepper motor driver as proposed from Roboshop.
Otherwise, if your load is changing, stepper motors are not good and servo motors are needed with a sensor measuring position like a potentiometer (to keep it simple). But then you need to close a speed control loop which means some feedback control knowledge. Again Roboshop is good place to look for equipment.
Turning into a spiral will require some knowledge of geometry. You need to get those two motors to turn at different speed then the robot turns into a circle. Try this first.
Then try a spiral: one motor has to keep its speed constant and the other has to gradually change its speed from 0 to a certain maximum being lower or equal than the other then, the radius of rotation of your motion will become larger and larger. You just need to adjust the speed update in order to adjust the radius. You can try to calculate that but trial an error can do as well.
Bests
LHR

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